High performance anti-block treatments for viscoelastic solids

ABSTRACT

Anti-blocking compositions are disclosed that include a wax or mixture of waxes effective to reduce, retard or prevent blocking of a viscoelastic solid when applied to the surface of such a solid. Also disclosed are methods of reducing, retarding or preventing blocking of a viscoelastic solid, and the products of those methods which are viscoelastic solids resistant to blocking.

PRIORITY CLAIMS

This application claims the benefit of U.S. Provisional Application No.62/052,745 filed Sep. 19, 2014.

TECHNICAL FIELD

The present disclosure is related to the field of viscoelastic materialswhich are supplied commercially as particulate solids. In particular,the tendency of bulk viscoelastic solids to agglomerate or block undercertain conditions of temperature and pressure affect their storage andmaterial handling properties. Preventing such blocking is anindustry-wide goal.

BACKGROUND

On a day-to-day basis, materials are commonly described as solids,liquids or gases; however, many commercially important products possesscharacteristics that are intermediate between those of an ideal solidand an ideal liquid. They are referred to as “viscoelastic materials,”whose physical characteristics are somewhat temperature dependent; theymay be described as viscoelastic solids (solid-like behavior dominates)or viscoelastic liquids (liquid-like behavior dominates). The presentdisclosure focuses on materials that are viscoelastic solids underambient conditions.

Viscoelastic solids are manufactured and supplied in a wide variety ofphysical forms, such as particles, flakes, fibers, granules, lozenges,pills, pellets, pastilles, prills, strings, ropes, filaments, troche,tablets or other forms dependent on the nature of the material and itsend-use. During manufacturing, a molten or liquid material is convertedto a viscoelastic solid, generally by cooling to ambient temperature.Agglomeration or blocking of the resultant viscoelastic solid product isa common problem during subsequent handling, processing, storage andtransport.

Significant compressive forces between individual particles may begenerated as a result of:

-   -   1. The mass of material within bulk storage or handling systems.    -   2. The mass of material within an individual package, as in a        bag, drum, bin or box.    -   3. Stacking bags or other compressible containers of the product        on top of each other, as on a pallet or in a warehouse.

Under such conditions, individual particles tend to adhere to oneanother, converting it from an easy-to-handle, easy-to-process,free-flowing particulate to an agglomerated mass resulting in a“blocked” product. Reduced efficiencies and added costs are a directconsequence of this agglomeration.

Blocking becomes more pronounced with increasing duration and magnitudeof the compressive forces as well as increased temperature. Thus, usingtemperature-controlled conditions during storage and transport minimizesthe problem, but increases costs to the producer and end-user.

BRIEF SUMMARY

The present disclosure addresses the blocking issues encountered with awide range of viscoelastic solids used for the formulation of adhesivesand coatings, as well as further-formulated products. Examples ofviscoelastic raw materials of interest include amorphous polyolefins,rosins, rosin acids, rosin esters, hydrogenated rosin esters, glycerolrosin esters, hydrogenated glycerol rosin esters, pentaerythritol rosinesters, hydrogenated pentaerythritol rosin esters, maleic modifiedrosins, phenolic modified rosins and other chemically modified rosins,aliphatic and cycloaliphatic hydrocarbon resins, hydrogenated aliphaticresins, aromatic resins, hydrogenated aromatic resins, terpene andpolyterpene resins, terpene-phenolic resins, alpha-methylstyrene resins,alpha-methylstyrene phenolic resins and styrene block copolymers. Endproducts may include, but are not necessarily limited to, hot meltadhesives, hot melt pressure sensitive adhesives, hot melt paints andthermoplastic elastomers.

One aspect of the present disclosure is directed to an anti-blockingcomposition including a wax or mixture of waxes effective to retard orprevent blocking of a viscoelastic solid when applied to the surface ofsuch a viscoelastic solid. In one embodiment, the anti-blockingcomposition is in the form of a water-based emulsion or dispersion. Inone embodiment, the dispersed phase, including a wax or mixture ofwaxes, includes about 20 weight % to about 50 weight % of the emulsionbased on the total weight of the emulsion. In one embodiment, theaverage wax particle size in the emulsion is about 100 nanometers toabout 50 microns.

In one embodiment, the anti-blocking composition further includes atleast one of a surfactant, a water-soluble polymeric material, a wettingagent (deposition aid), or mixtures thereof. The surfactant provides fora stable water based emulsion or dispersion, whereas the water-solublepolymeric material adheres the wax, or mixture of waxes, to the surfaceof the viscoelastic solid and provides a useful barrier to the diffusionof low and high molecular weight materials. The wetting agent/depositionaid assists in depositing the wax, or mixture of waxes, onto theviscoelastic solid. The addition of one or more of a surfactant, awater-soluble polymeric material, or a wetting agent, eitherindividually or in combination, does not affect the thermal or physicalstability of the molten state of a viscoelastic solid to which theanti-blocking composition has been applied. In one embodiment, theanti-blocking composition contains a surfactant in an amount of about0.5 to about 10.0 weight % based on the total weight of theanti-blocking composition. In another embodiment, the anti-blockingcomposition contains a water-soluble polymeric material in an amount ofabout 0.2 to about 5.0 weight % based on the total weight of theanti-blocking composition. In another embodiment, the anti-blockingcomposition contains a wetting agent (deposition aid) in an amount ofabout 0.05 to about 0.50 weight % based on the total weight of theanti-blocking composition. In terms of dry weight, the wax or mixture ofwaxes includes about 75% or more by weight of the dry components.

Suitable anti-blocking waxes for use in one or more aspects of thepresent disclosure are selected from the group consisting of polyolefinhomopolymers, oxidized polyolefin homopolymers, ethylene-vinyl acetatecopolymers, ethylene-acrylate copolymers, maleic anhydride-graftedpolyolefins and mixtures thereof. In some embodiments, the polyolefinhomopolymers are selected from polyethylene homopolymers; the oxidizedpolyolefin homopolymers are selected from oxidized polyethylenehomopolymers; the ethylene-acrylate copolymers are selected from theethylene-acrylic acid copolymers; and the maleic anhydride-graftedpolyolefins are selected from maleic anhydride-grafted polyethylenes andmaleic anhydride-grafted polypropylenes.

The anti-blocking wax or mixture of waxes typically has a weight averagemolecular weight of about 1000 to about 15000 Daltons. In someembodiments, the weight average molecular weight ranges from about 1000to about 10000 Daltons, or about 3000 to about 7000 Daltons. In oneembodiment, the weight average molecular weight of the wax is about 6000Daltons.

Yet another aspect of the disclosure is directed to a method ofreducing, retarding or preventing blocking of a viscoelastic solid,including the steps of:

-   -   a) treating the surface of a viscoelastic solid after        manufacture with the above anti-blocking composition; and    -   b) drying to produce a viscoelastic solid coated with the        anti-blocking composition.

In one embodiment of this method, the anti-blocking composition is inthe form of an aqueous emulsion. In another embodiment, theanti-blocking composition is in the form of an aqueous dispersion. Thesemethods are referred to collectively as the Emulsion Surface CoatingStrategy. The average wax particle size in the emulsion is about 100nanometers to about 50 microns.

In some embodiments of these methods, the wax or wax mixture is selectedfrom the group consisting of polyethylene homopolymers, oxidizedpolyethylene homopolymers, ethylene-vinyl acetate copolymers,ethylene-acrylic acid copolymers, maleic anhydride-grafted polyethylene,maleic anhydride-grafted polypropylene and mixtures thereof.

In some embodiments of these methods, the viscoelastic solid is selectedfrom the group consisting of a hot melt adhesive, a hot meltpressure-sensitive adhesive, a hot melt paint and a thermoplasticelastomer. Alternatively, the viscoelastic solid can be selected fromthe group consisting of amorphous polyolefins, rosins, rosin acids,rosin esters, hydrogenated rosin esters, glycerol rosin esters,hydrogenated glycerol rosin esters, pentaerythritol rosin esters,hydrogenated pentaerythritol rosin esters, maleic modified rosins,phenolic modified rosins and other chemically modified rosins, aliphaticand cycloaliphatic hydrocarbon resins, hydrogenated aliphatic resins,aromatic resins, hydrogenated aromatic resins, terpene and polyterpeneresins, terpene-phenolic resins, alpha-methylstyrene resins,alpha-methylstyrene phenolic resins, styrene block copolymers andmixtures thereof.

In some embodiments of these methods, the viscoelastic solid is in theform of particles, flakes, fibers, granules, lozenges, pills, pellets,pastilles, prills, strings, ropes, filaments, troche or tablets.

Still another aspect of the disclosure is directed to a viscoelasticsolid that is resistant to blocking and is produced by the EmulsionSurface Coating Strategy described above, where the surface of theviscoelastic solid is coated with an anti-blocking wax or mixture ofwaxes, and one or more of a surfactant, a water-soluble polymericmaterial, or a wetting agent (deposition aid). The water-solublepolymeric material adheres the wax, or mixture of waxes, to the surfaceof the viscoelastic solid and provides a useful barrier to the diffusionof low and high molecular weight materials. Addition of one or more of asurfactant, a water-soluble polymeric material or a wetting agent(deposition agent), either individually or in combination, to ananti-blocking wax emulsion or dispersion, and coating a viscoelasticsolid with the emulsion or dispersion provides a coated solid which ischaracterized in that the molten state of the coated viscoelastic solidretains the thermal and physical stability of the uncoated viscoelasticsolid. In other words, the anti-blocking wax, surfactant, water-solublepolymeric material, and wetting agent, either individually or incombination, do not affect the thermal or physical stability of themolten state of a viscoelastic solid to which the anti-blockingcomposition has been applied. In one embodiment the coated viscoelasticsolid contains the surfactant in about 0.002 to about 0.25 weight %based on the total weight of the anti-blocking composition. In anotherembodiment the coated viscoelastic solid contains the water-solublepolymeric material in about 0.001 to about 0.15 weight % based on thetotal weight of the anti-blocking composition. In another embodiment thecoated viscoelastic solid contains the wetting agent/deposition aid inabout 0.0002 to about 0.01 weight % based on the total weight of theanti-blocking composition.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the inventive subject matter or the applicationand uses of the inventive subject matter. Furthermore, there is nointention to be bound by any theory presented in the precedingbackground or the following detailed description.

Understanding the underlying technical causes of blocking ofviscoelastic solids has led to a surprising and unexpected solution thatreduces or prevents blocking which can be employed in providingviscoelastic solids that are resistant to blocking: After formingviscoelastic particles, treating the viscoelastic particulates' surfacewith an anti-blocking composition including an anti-blocking wax ormixture of waxes, herein referred to as the “Surface Coating Strategy”or more specifically, the “Emulsion Surface Coating Strategy.” Theanti-blocking wax/wax mixture retards or prevents blocking of theviscoelastic solid, and the treatment of the viscoelastic solid isperformed at a point in the manufacturing process following formation ofthe desired particulate morphology but before packaging of the productinto bags, sacks, drums or other containers.

Existing emulsion treatments for viscoelastic solids are known tocompromise the characteristics of materials in both their molten andsolid states; in particular, the thermal stability and rheologicalbehavior can be compromised. The anti-blocking compositions of thepresent disclosure, including emulsion compositions and dispersioncompositions, do not modify the thermal stability or rheologicalbehavior of the treated material, and the compositions further includecomponents that facilitate the effective wetting of the particulatesurface and effect a barrier, thereby improving the shelf-stability ofmaterials vulnerable to hydrolysis or oxidation.

With regard to treatment of a particulate viscoelastic solid withemulsion compositions, one embodiment of the present disclosureconsidered the thermal stability of two hot melt adhesives, TechnomeltSupra 130 and Technomelt Supra 145 (available from Henkel, Dusseldorf,Germany). The use of the following components, from which emulsions maybe formulated, has been found to not compromise the thermal stability ofthe adhesives (assessed at 170° C.):

Component Type PE Homopolymer wax Oxidized High Density PE waxEthylene-Vinyl Acetate Copolymer wax Oxidized Low Density PE waxEthylene-Acrylic Acid Copolymer wax TAM-2 ™ Cationic Surfactantsurfactant/wetting agent Tergitol ™ 15-S-12 Non-Ionic Surfactantsurfactant/wetting agent Siltech ™ A008-UP Silicone Polyether wettingagent Kuraray ™ Poval 25-88KL water soluble polymer Diethylaminoethanolbase for pH control NH₄OH base for pH control Citric acid acid for pHcontrol Oleic acid acid for pH control

One aspect of the present disclosure is directed to an anti-blockingcomposition including a wax or mixture of waxes effective to retard orprevent blocking of a viscoelastic solid when applied to the surface ofsuch a viscoelastic solid. In certain preferred embodiments, theanti-blocking composition is in the form of a water-based emulsion ordispersion. Where the emulsion is an oil-in-water emulsion containing adispersed wax phase and a continuous aqueous phase. Where the dispersionis a suspension of a micronized wax in an aqueous medium. In oneembodiment, the dispersed phase, including a wax or mixture of waxes,includes about 20 weight % to about 50 weight % of the emulsion based onthe total weight of the anti-blocking composition. In certain preferredembodiments, the average wax particle size in the emulsion is about 100nanometers to about 50 microns. In one embodiment the D₅₀ of the waxparticles is about 500 nanometers to about 25 microns. In anotherembodiment the D₅₀ of the wax particles is about 750 nanometers to about15 microns. Particle size is determined using a Microtrac™ S3500 LaserDiffraction Particle Size Analyzer (Microtrac, Largo, Fla., UnitedStates).

At the D₅₀ value, which is also known as the median diameter or themedium value, of the cumulative particle size distribution 50% ofparticles are smaller than and 50% of the particles are larger than thestated value. For example, if D₅₀=5 microns, then 50% of the particlesin the sample are larger than 5 microns and 50% smaller than 5 microns.Any method of determining the D₅₀ value may be used in the art,including, but not limited to, the use of a particle analyzer.

In one embodiment the anti-blocking composition further includes atleast one of a surfactant or mixture of surfactants, a water-solublepolymeric material or mixture of water-soluble polymeric materials, anda wetting agent (deposition aid) or a mixture of wettingagents/deposition aids. The surfactant or mixture of surfactantsprovides for a stable water based composition. The water-solublepolymeric material or mixture of water-soluble polymers adheres the waxor mixture of waxes to the surface of the viscoelastic solid, andprovides an effective barrier against the ingress or egress of low andhigh molecular weight materials, thereby facilitating improvedshelf-stability of the coated viscoelastic solid. The wetting agent (ordeposition aid), or mixture of wetting agents/deposition aids, assistsin the deposition of the wax or mixture of waxes onto the viscoelasticsolid. These anti-blocking composition components, either individuallyor in combination, do not affect the thermal or physical stability ofthe molten state of a viscoelastic solid to which the anti-blockingcomposition has been applied prior to melting. In one embodiment theanti-blocking composition contains surfactant in about 0.5 to about 10.0weight % based on the total composition. In another embodiment theanti-blocking composition contains water-soluble polymeric material inabout 0.2 to about 5.0 weight % based on the total composition. Inanother embodiment the anti-blocking composition contains wettingagent/deposition aid in about 0.05 to about 0.50 weight % based on thetotal composition. In a further embodiment, the anti-blockingcomposition includes surfactant in about 1.0 to about 5.0 weight %,water-soluble polymeric material in about 0.5 to about 2.0 weight %, andwetting agent/deposition aid in about 0.05 to about 0.25 weight %, basedon the total composition. In terms of dry weight, the wax or mixture ofwaxes includes about 75% or more by weight of the dry components.

Suitable waxes are selected from the group consisting of polyolefinhomopolymers, oxidized polyolefin homopolymers, ethylene-vinyl acetatecopolymers, ethylene-acrylate copolymers, maleic anhydride-graftedpolyolefins and mixtures thereof. In preferred embodiments, thepolyolefin homopolymers are selected from polyethylene homopolymers; theoxidized polyolefin homopolymers are selected from oxidized polyethylenehomopolymers; the ethylene-acrylate copolymers are selected from theethylene-acrylic acid copolymers; and the maleic anhydride-graftedpolyolefins are selected from maleic anhydride-grafted polyethylenes andmaleic anhydride-grafted polypropylenes.

Polyethylene homopolymers, oxidized polyethylene homopolymers,polypropylene homopolymers, ethylene-vinyl acetate copolymers andethylene-acrylic acid copolymers are particularly useful waxes inemulsions and dispersions used in surface coating (Surface CoatingStrategy). Maleic anhydride-grafted polyethylenes and maleicanhydride-grafted polypropylenes are also useful.

The wax or mixture of waxes typically has a weight average molecularweight of about 1000 to about 15000 Daltons. In one embodiment, theweight average molecular weight ranges from about 1000 to about 10000Daltons. In another embodiment the weight average molecular weightranges from about 3000 to about 7000 Daltons. In one embodiment, theweight average molecular weight of the wax is about 6000 Daltons.

Another aspect of the disclosure is directed to a method of reducing,retarding or preventing blocking of a viscoelastic solid, including thesteps of coating the surface of a particulate viscoelastic solid withthe above anti-blocking composition. The coated anti-blocking solid isthen dried, thereby providing a viscoelastic solid surface-coated withthe anti-blocking composition components. In this Emulsion SurfaceCoating Strategy, the treating step may include treating the surface ofa particulate viscoelastic solid or a viscoelastic solid article with aliquid composition to give a continuous coating of the anti-blocktreatment over the viscoelastic solid. In one embodiment, the dryingstep may include drying with the application of heat (below the meltingor softening point of the viscoelastic solid) and/or vacuum, with orwithout passing a drying gas such as air over the surface of the treatedviscoelastic solid article or through the treated particulate solid.Such processes provide an article or particulate solid whose core is theviscoelastic solid that is substantially covered by an anti-blockingcoating. As used herein, the term “substantially” indicates more thanhalf or greater than 50%, preferably at least about 75%, more preferablyat least about 85%, still more preferably at least about 95%, and mostpreferably essentially 100%.

The anti-blocking wax or wax mixture is preferably selected from thegroup consisting of polyethylene homopolymers, oxidized polyethylenehomopolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acidcopolymers, maleic anhydride-grafted polyethylene, maleicanhydride-grafted polypropylene and mixtures thereof.

The viscoelastic solid is preferably selected from the group consistingof a hot melt adhesive, a hot melt pressure-sensitive adhesive, a hotmelt paint and thermoplastic elastomers. Alternatively, the viscoelasticsolid can be selected from the group consisting of amorphouspolyolefins, rosins, rosin acids, rosin esters, hydrogenated rosinesters, glycerol rosin esters, hydrogenated glycerol rosin esters,pentaerythritol rosin esters, hydrogenated pentaerythritol rosin esters,maleic modified rosins, phenolic modified rosins and other chemicallymodified rosins, aliphatic and cycloaliphatic hydrocarbon resins,hydrogenated aliphatic resins, aromatic resins, hydrogenated aromaticresins, terpene and polyterpene resins, terpene-phenolic resins,alpha-methylstyrene resins, alpha-methylstyrene phenolic resins, styreneblock copolymers and mixtures thereof.

The viscoelastic solid is preferably in the form of particles, flakes,fibers, granules, lozenges, pills, pellets, pastilles, prills, strings,ropes, filaments, troche, tablets or combinations thereof.

For the emulsion surface coating strategy, incorporation levels of theanti-blocking wax or mixture of waxes can be as low as about 0.2 partsof an emulsion containing 40% solids in 100.00 parts viscoelastic solid,which equates to about 0.08 parts solids in 100.0 parts viscoelasticsolid. Perhaps, the upper limit will be limited by cost and/or technicalrequirements.

Still another aspect of the disclosure is directed to a viscoelasticsolid resistant to blocking which is the product of the Emulsion SurfaceCoating Strategy, where the surface of the viscoelastic solid is coatedwith an anti-blocking wax or mixture of waxes, and one or more of asurfactant or mixture of surfactants, a water-soluble polymeric materialor mixture of water-soluble polymeric materials, or a wetting agent(deposition aid) or mixture of wetting agents/deposition aids. Thewater-soluble polymeric material or mixture of water-soluble polymersadheres the wax or mixture of waxes to the surface of the viscoelasticsolid, and provides an effective barrier against the ingress or egressof low and high molecular weight materials. The surfactant or mixture ofsurfactants, water-soluble polymeric material or mixture ofwater-soluble polymeric materials, and the wetting agent (depositionaid) or mixture of wetting agents/deposition aids, either individuallyor in combination, do not affect the thermal or physical stability ofthe coated viscoelastic solid when melted. In one embodiment the coatedviscoelastic solid contains surfactant in about 0.002 to about 0.25weight % based on the total weight. In another embodiment the coatedviscoelastic solid contains water-soluble polymeric material in about0.001 to about 0.15 weight % based on the total weight. In anotherembodiment the coated viscoelastic solid contains wettingagent/deposition aid in about 0.0002 to about 0.01 weight % based on thetotal weight. In a further embodiment the coated viscoelastic solidcontains surfactant in about 0.004 to about 0.125 weight %,water-soluble polymeric material in about 0.002 to about 0.08 weight %,and wetting agent/deposition aid in about 0.0002 to about 0.05 weight %,based on the total weight.

ILLUSTRATIVE EXAMPLES

The present disclosure is now illustrated by the following non-limitingexamples. It should be noted that various changes and modifications canbe applied to the following examples and processes without departingfrom the scope of this disclosure, which is defined in the appendedclaims. Therefore, it should be noted that the following examples shouldbe interpreted as illustrative only and not limiting in any sense.

Example 1 Undesirable Blocking of Viscoelastic Solids

The tendency of a number of pelletized viscoelastic solids to blockduring storage and transport was evaluated. The products consideredwere:

a. Styrene-butadiene-styrene block copolymer Calprene 401 (Dynasol,Spain).b. Styrene-butadiene-styrene block copolymer Calprene 540 (Dynasol,Spain).c. Styrene-butadiene-styrene block copolymer Solprene 4318 (Dynasol,Spain).d. Hot melt adhesive Technomelt Supra 130 (Henkel, Germany).e. Hot melt adhesive Technomelt Supra 145 (Henkel, Germany).f. Thermoplastic elastomer Marfran E CST1381 (Franceschetti, Italy).

In each case 100 grams of the pelletized product was placed into an opentopped plastic container, which had been lined with a silicone coatedrelease liner (with the silicone coated surface innermost), where thecontainer had a flat circular base and straight sides. The chosencontainers had an approximate diameter of 6.5 centimeters and height of10.0 centimeters. A protective disc of silicone coated release liner wasthen placed on top of the pellets (with the coated surface againstthem). A 2 kilogram laboratory weight, whose dimensions were wellmatched to those of the container, was then carefully placed on the topof the uppermost disc of silicone coated release liner to provide areproducible compressive force (to simulate that experienced within anactual stacked bag or sack). The weighted container was then placed in alaboratory oven set at 40° C. for a controlled period of time.Sufficient samples were prepared to allow evaluation after differenttest times. After the desired time had elapsed the container was removedfrom the oven and the weight with protective disc of silicone coatedrelease liner promptly removed. The container was then inverted and theease of discharging the pellets observed. The spontaneous flow ofpellets is desired or at least that such a flow is possible onapplication of a light knock only to the base of the container; this isdescribed as free-flow. However, when the individual pellets have formedan agglomerated mass and cannot be readily disrupted to give afree-flowing mass. The product is said to be blocked.

The behavior of the products was considered after 3 hours and 3 daysageing under the specified conditions; see table 1.

TABLE 1 Blocking of Viscoelastic Solids Observation Viscoelastic Solid 3Hours 3 Days Calprene 401 Free-Flow Blocked Calprene 540 Free-FlowBlocked Solprene 4318 Free-Flow Blocked Technomelt Supra 130 BlockedBlocked Technomelt Supra 145 Free-Flow Free-Flow Marfran E CST1381Blocked Blocked

The results illustrate the tendency of pelletized viscoelastic solids tobecome blocked within their packaging prior to use with 2 productsfailing within 3 hours and only 1 product remaining free-flowing after 3days. The susceptibility of the Technomelt Supra 130 hot melt adhesiveto rapidly block was then exploited to speed product development asillustrated in the subsequent examples.

Example 2 Preparation of Aqueous Homopolymer Dispersions and Treatmentof Hot Melt Adhesive

Aqueous dispersions of micronized polyethylene waxes were prepared andused to treat a hot melt adhesive, whose blocking tendency was thendetermined.

Micronized samples of a synthetic polyethylene wax (drop point: 126° C.,density: 0.96 g/cm³) were prepared at a mean particle size of 6 micronsand 18 microns. These micronized waxes were then dispersed in an aqueoussolution of polyvinyl alcohol, non-ionic surfactant and isopropylalcohol with high shear mixing. Where the chosen polyvinyl alcohol wasPoval 25-88KL (Kuraray Europe, Germany) and non-ionic surfactant wasTergitol 15-S-5 (Dow Chemical, USA). Their formulation is described intable 2.

TABLE 2 Micronized Polyethylene Wax Dispersion Component Weight (%)Micronized Polyethylene Wax 20.0 Poval 25-88KL 1.5 Tergitol 15-S-5 1.0Water 73.5 Isopropyl Alcohol 4.00

A hot melt adhesive, Technomelt Supra 130 (Henkel, Germany), was thentreated with the wax dispersions.

Adhesive pellets (500 grams) were weighed into an epoxy lined paint canand sufficient wax dispersion added to give the desired treatment level.In this example treatment levels of 0.2% and 0.5% were applied, whichequates to 5.0 grams and 12.5 grams of wax dispersion respectively. Thepaint cans were sealed and then placed on a bottle roller for 15 minutesto ensure a uniform distribution of the treatment over the surface ofthe pellets. The pellets were then decanted onto a silicone coatedrelease liner, distributed so as to avoid any significant contact andallowed to dry overnight under ambient laboratory conditions.

Their tendency to block was determined according to the method describedin example 1. The results are reported in table 3.

TABLE 3 Blocking Tendency of Technomelt Supra 130 (Aged: 3 Hours)Synthetic Polyethylene Wax Mean Particle Size Treatment Level (%)(Microns) 0.2 0.5 6 Free-Flow Free-Flow 18 Free-Flow Free-Flow

The treated adhesive pellets were found to remain free-flowing, whileblocking of untreated ones under the same test conditions is reported inexample 1.

Example 3 Preparation of Aqueous Homopolymer Dispersions and Treatmentof Hot Melt Adhesive

Aqueous dispersions of micronized polyethylene waxes were prepared andused to treat a hot melt adhesive, whose blocking tendency was thendetermined.

A micronized sample of a synthetic polyethylene wax (drop point: 126°C., density: 0.96 g/cm³) was prepared at a mean particle size of 18microns. The micronized wax was then dispersed in an aqueous solution ofpolyvinyl alcohol with high shear mixing, in which isopropyl alcohol andoptionally a silicone glycol were included. The chosen polyvinyl alcoholwas Poval 25-88KL (Kuraray Europe, Germany) and the silicone glycol wasSilsurf A0008UP (Siltech Corporation, Canada). Their formulations aredescribed in table 4.

TABLE 4 Micronized Polyethylene Wax Dispersion Weight (%) ComponentDispersion A Dispersion B Micronized Polyethylene Wax 20.00 20.00 Poval25-88KL 1.25 1.25 Silsurf A0008UP 0.00 1.00 Water 74.75 73.75 IsopropylAlcohol 4.00 4.00

A hot melt adhesive, Technomelt Supra 130 (Henkel, Germany), was thentreated with the wax dispersions.

Adhesive pellets (500 grams) were weighed into an epoxy lined paint canand sufficient wax dispersion added to give the desired treatment level.In this example treatment levels of 0.2% and 0.5% were applied, whichequates to 5.0 grams and 12.5 grams of wax dispersion respectively. Thepaint cans were sealed and then placed on a bottle roller for 15 minutesto ensure a uniform distribution of the treatment over the surface ofthe pellets. The pellets were then decanted onto a silicone coatedrelease liner, distributed so as to avoid any significant contact andallowed to dry overnight under ambient laboratory conditions.

Their tendency to block was determined according to the method describedin example 1. The results are reported in table 5.

TABLE 5 Blocking Tendency of Technomelt Supra 130 (Aged: 3 Hours)Treatment Level (%) Treatment 0.2 0.5 Dispersion A Free-Flow Free-FlowDispersion B Free-Flow Free-Flow

The treated adhesive pellets were found to remain free-flowing, whileblocking of untreated ones under the same test conditions is reported inexample 1.

Example 4 Preparation of Aqueous Oxidized Homopolymer Dispersions andTreatment of Hot Melt Adhesive

Aqueous dispersions of micronized oxidized polyethylene waxes wereprepared and used to treat a hot melt adhesive, whose blocking tendencywas then determined.

Micronized samples of a synthetic oxidized polyethylene wax (drop point:137° C., density: 0.99 g/cm³) were prepared at a mean particle size of12 microns and 45 microns. These micronized waxes were then dispersed inan aqueous solution of polyvinyl alcohol, non-ionic surfactant andisopropyl alcohol with high shear mixing. Where the chosen polyvinylalcohol was GohsenX T-330H (Nippon Gohsei, Japan) and the non-ionicsurfactant was Tergitol 15-S-5 (Dow Chemical, USA). Their formulation isdescribed in table 6.

TABLE 6 Micronized Oxidized Polyethylene Wax Dispersion Component Weight(%) Micronized Oxidized Polyethylene 20.0 Wax GohsenX T-330H 1.5Tergitol 15-S-5 1.0 Water 73.5 Isopropyl Alcohol 4.00

A hot melt adhesive, Technomelt Supra 130 (Henkel, Germany), was thentreated with the wax dispersions.

Adhesive pellets (500 grams) were weighed into an epoxy lined paint canand sufficient wax dispersion added to give the desired treatment level.In this example a treatment level of 0.5% was applied, which equates to12.5 grams of wax dispersion. The paint cans were sealed and then placedon a bottle roller for 15 minutes to ensure a uniform distribution ofthe treatment over the surface of the pellets. The pellets were thendecanted onto a silicone coated release liner, distributed so as toavoid any significant contact and allowed to dry overnight under ambientlaboratory conditions.

Their tendency to block was determined according to the method describedin example 1. The results are reported in table 7.

TABLE 7 Blocking Tendency of Technomelt Supra 130 (Aged: 3 Hours)Synthetic Oxidized Polyethylene Wax Mean Particle Size (Microns)Observation 12 Free-Flow 45 Free-Flow

The treated adhesive pellets were found to remain free-flowing, whileblocking of untreated ones under the same test conditions is reported inexample 1.

Example 5 Preparation of Aqueous Oxidized Homopolymer Dispersions andTreatment of Hot Melt Adhesive

An aqueous dispersion of a micronized oxidized polyethylene wax wasprepared and used to treat a hot melt adhesive, whose blocking tendencywas then determined.

A micronized sample of a synthetic oxidized polyethylene wax (droppoint: 137° C., density: 0.99 g/cm³) was prepared at a mean particlesize of 12 microns. The micronized wax was then dispersed in an aqueoussolution of silicone glycol and isopropyl alcohol with high shearmixing, where the chosen silicone glycol was Silsurf A0008UP (SiltechCorporation, Canada). Its formulation is described in table 8.

TABLE 8 Micronized Oxidized Polyethylene Wax Dispersion Component Weight(%) Micronized Oxidized Polyethylene 20.00 Wax Silsurf A0008UP 0.25Water 75.75 Isopropyl Alcohol 4.00

A hot melt adhesive, Technomelt Supra 130 (Henkel, Germany), was thentreated with the wax dispersion.

Adhesive pellets (500 grams) were weighed into an epoxy lined paint canand sufficient wax dispersion added to give the desired treatment level.In this example treatment levels of 0.2% and 0.5% were applied, whichequates to 5.0 grams and 12.5 grams of wax dispersion respectively. Thepaint cans were sealed and then placed on a bottle roller for 15 minutesto ensure a uniform distribution of the treatment over the surface ofthe pellets. The pellets were then decanted onto a silicone coatedrelease liner, distributed so as to avoid any significant contact andallowed to dry overnight under ambient laboratory conditions.

Their tendency to block was determined according to the method describedin example 1. The results are reported in table 9.

TABLE 9 Blocking Tendency of Technomelt Supra 130 (Aged: 3 Hours and 3Days) Observation Treatment Level (%) 3 Hours 3 Days 0.2 Free-FlowFree-Flow 0.5 Free-Flow Free-Flow

The treated adhesive pellets were found to remain free-flowing, whileblocking of untreated ones under the same test conditions is reported inexample 1.

Example 6 Preparation of Controlled Particle Size Wax Emulsions ofHomopolymer and Copolymer

Examples 2, 3, 4 and 5 describe the initial preparation of a micronizedwax, at a controlled particle size, that is then dispersed in water withother components. This example illustrates the preparation of acontrolled particle size product through emulsification of polyethylenehomopolymer and ethylene acrylic acid copolymer waxes combined with avolatile organic base, which effects the in-situ conversion of thecopolymer to its soap, and water.

Samples were prepared with a polyethylene homopolymer (drop point: 101°C., density: 0.91 g/cm³), an ethylene acrylic acid copolymer (droppoint: 92° C., density: 0.94 g/cm³, acid number: 120 mgKOH/g),2-dimethylaminoethanol and water according to the formulations describedin table 10.

TABLE 10 Mixed Homopolymer-Copolymer Emulsion Weight (%) ComponentEmulsion A Emulsion B Polyethylene Homopolymer 8.0 8.0 Ethylene AcrylicAcid 32.0 32.0 Copolymer 2-Dimethylaminoethanol 1.4 1.2 Water 58.6 58.8

The emulsions may be prepared by either a direct process or a dilutionprocess.

When a direct process is used, all of the components (polyethylenehomopolymer, ethylene acrylic acid copolymer, 2-dimethylaminoethanol andall the water) are charged into a suitable stainless steel high pressurereactor, which is then securely sealed. With high shear mixing theformulation is heated to 110° C. This temperature is maintained for afurther 30 minutes with continuous high shear mixing. The mix speed isthen reduced, low shear mixing condition, and the product cooled to roomtemperature.

For a dilution process the polyethylene homopolymer, ethylene acrylicacid copolymer, 2-dimethylaminoethanol and 45% of the total water arefirst charged into a stainless steel high pressure reactor, which isthen sealed. With high shear mixing the contents of the reactor areheated to 110° C. and maintained at this temperature for 30 minutes. Thebalance of the water, i.e. 55% of the total water, is then injected intothe reactor. Maintaining product temperature between 95° C. and 110° C.high shear mixing is continued for a further 10 minutes before reducingthe mix speed, low shear mixing conditions, and the product cooled toroom temperature.

The particle size distribution of the resulting emulsions was determinedusing a Microtrac S3500 Laser Diffraction Particle Size Analyzer(Microtrac, USA) and their 50 percentile values were recorded. For bothemulsions a desirable and controlled particle size was achieved; 9.9microns for emulsion A and 12.7 microns for emulsion B.

Example 7 Preparation of Controlled Particle Size Wax Emulsions ofOxidized Homopolymer and Copolymer

Examples 2, 3, 4 and 5 describe the initial preparation of a micronizedwax, at a controlled particle size, that is then dispersed in water withother components. This example illustrates the preparation of acontrolled particle size product through emulsification of a mixture ofan oxidized polyethylene homopolymer and an ethylene acrylic acidcopolymer combined with a volatile organic base, which effects thein-situ conversion of the copolymer to its soap, and water.

In this case samples were prepared with an oxidized polyethylenehomopolymer (drop point: 108° C., density: 0.93 g/cm³), an ethyleneacrylic acid copolymer (drop point: 92° C., density: 0.94 g/cm³, acidnumber: 120 mgKOH/g), 2-dimethylaminoethanol and water according to theformulations described in table 11.

TABLE 11 Mixed Oxidized Homopolymer-Copolymer Emulsion Weight (%)Component Emulsion X Emulsion Y Oxidized Polyethylene 22.50 22.50Homopolymer Ethylene Acrylic Acid 7.50 7.50 Copolymer2-Dimethylaminoethanol 1.80 1.35 Water (Part 1) 23.65 23.65 Water (Part2) 45.00 45.00

The emulsions were prepared via a dilution process, in which the watercharge is split in to 2 parts.

The oxidized polyethylene homopolymer, ethylene acrylic acid copolymer,2-dimethylaminoethanol and the first part of the water, water (part 1),are first charged into a stainless steel high pressure reactor, that isthen securely sealed. With high shear mixing the contents of the reactorare heated to 110° C. and maintained at this temperature for 30 minutes.The remainder of the water, water (part 2), is then injected into thereactor. Maintaining the temperature between 95° C. and 110° C. highshear mixing is continued for a further 10 minutes before reducing themix speed, low shear mixing conditions, and the product cooled to roomtemperature.

The particle size distribution of the resulting emulsions was determinedusing a Microtrac S3500 Laser Diffraction Particle Size Analyzer(Microtrac, USA) and their 50 percentile values were recorded. For bothemulsions a desirable and controlled particle size was achieved; 100nanometers for emulsion X and 150 nanometers for emulsion Y.

Example 8 Performance Characteristics of a Mixed Homopolymer-CopolymerEmulsion (Emulsion B)

This example considers the performance characteristics of emulsion B,whose formulation, preparation and particle size characteristics aredescribed in example 6. A hot melt adhesive, Technomelt Supra 130(Henkel, Germany), was treated with this emulsion.

Adhesive pellets (500 grams) were weighed into an epoxy lined paint canand sufficient emulsion added to give the desired treatment level. Inthis example treatment levels of 0.2% and 0.5% were applied, that equateto 2.50 grams and 6.25 grams of emulsion respectively. The paint canswere sealed and then placed on a bottle roller for 15 minutes to ensurea uniform distribution of the treatment over the surface of the pellets.The pellets were then decanted onto a silicone coated release liner,distributed so as to avoid any significant contact and allowed to dryovernight under ambient laboratory conditions.

Their tendency to block was determined according to the method describedin example 1. The results are reported in table 12.

TABLE 12 Blocking Tendency of Technomelt Supra 130 (Aged: 3 Hours)Treatment Level (%) Observation 0.2 Free-Flow 0.5 Free-Flow

The treated adhesive pellets were found to remain free-flowing, whileblocking of untreated ones under the same test conditions is reported inexample 1.

Example 9 Performance Characteristics of a Mixed OxidizedHomopolymer-Copolymer Emulsion (Emulsion x)

This example considers the performance characteristics of emulsion X andemulsion Y, whose formulation, preparation and particle sizecharacteristics are described in example 7. A hot melt adhesive,Technomelt Supra 130 (Henkel, Germany), was treated with this emulsion.

Adhesive pellets (500 grams) were weighed into an epoxy lined paint canand sufficient emulsion added to give the desired treatment level. Inthis example a treatment level of 0.2% was applied, which equates to3.33 grams of emulsion. The paint cans were sealed and placed on abottle roller for 15 minutes to ensure a uniform distribution of thetreatment over the surface of the pellets. The pellets were thendecanted onto a silicone coated release liner, distributed so as toavoid any significant contact and allowed to dry overnight under ambientlaboratory conditions.

Their tendency to block was determined according to the method describedin example 1. The results are reported in table 13.

TABLE 13 Blocking Tendency of Technomelt Supra 130 (Aged: 3 Hours)Emulsion Observation X Free-Flow Y Free-Flow

The treated adhesive pellets were found to remain free-flowing, whileblocking of untreated ones under the same test conditions is reported inexample 1.

Example 10 Melt Stability of Untreated and Treated Hot Melt Adhesive

As the surface treatment of the hot melt adhesive must not compromiseits processing characteristics under end-use conditions, it is importantto understand the melt characteristics of untreated and treated product.In order to mimic the conditions experienced during their commercial usemolten adhesive samples were aged for 7 days at 170° C. (in air). Theirmelt characteristics were then evaluated and any differences withrespect to an untreated control noted.

In this example the melt stability of untreated and treated TechnomeltSupra 130 (Henkel, Germany) was evaluated, where the treated sampleswere prepared with an oxidized polyethylene wax dispersion (per example5) as well as a mixed homopolymer-copolymer emulsion, emulsion B, perexample 6. Pellets with treatment levels of 0.2% and 0.5% wereconsidered.

In each case adhesive pellets (100 grams) were placed in a cleanaluminum foil dish. A second clean aluminum foil dish was then invertedover the first one and secured with 3 or 4 paper clips to protect theproduct from any extraneous contamination. The dishes were then placedin a laboratory oven, equilibrated at 170° C., for 7 days. The sampleswere removed from the oven at the scheduled time and the covering dishesremoved to permit evaluation of the molten adhesive.

First a visual assessment for bulk and surface appearance, includingcolor change, as well as the presence of any gels or precipitate wasperformed. Then the flow characteristics were evaluated qualitatively toensure that the sample was able to flow smoothly (undisturbed by anysurface skinning or gelation). An overall conclusion, PASS or FAIL, wasdetermined from these observations. The results are reported in table14.

TABLE 14 Melt Stability of Treated and Untreated Hot Melt AdhesiveTreatment oxidized polyethylene homopolymer-copolymer Treatment waxdispersion emulsion; emulsion B Level (%) (per example 5) (per example6) 0.0 (Control) PASS PASS 0.2 PASS PASS 0.5 PASS PASS

Although some enhanced color development was noted with the treatedadhesive pellets, in all other respects the melt characteristics of thetreated products could not be differentiated from those of the control.Thus processing characteristics of the hot melt adhesive are independentof the surface treatment applied.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the inventive subject matter, itshould be appreciated that a vast number of variations exist. It shouldalso be appreciated that the exemplary embodiment or exemplaryembodiments are only examples, and are not intended to limit the scope,applicability, or configuration of the inventive subject matter in anyway. Rather, the foregoing detailed description will provide thoseskilled in the art with a convenient road map for implementing anexemplary embodiment of the inventive subject matter. It beingunderstood that various changes may be made in the function andarrangement of elements described in an exemplary embodiment withoutdeparting from the scope of the inventive subject matter as set forth inthe appended claims.

What is claimed is:
 1. An anti-blocking composition comprising at leastone wax in an amount effective to reduce blocking of a viscoelasticsolid when said composition is applied to the surface of saidviscoelastic solid.
 2. The anti-blocking composition of claim 1 in theform of a water-based emulsion or dispersion.
 3. The anti-blockingcomposition of claim 2, wherein said at least one wax comprises about 20weight % to about 50 weight % of said water-based emulsion or dispersionon the total weight of the emulsion or dispersion.
 4. The anti-blockingcomposition of claim 1, further comprising at least one of the materialsselected from: a. a surfactant, b. a water-soluble polymeric material,and c. a wetting agent; wherein the molten state of a viscoelastic solidcoated with said anti-blocking composition retains the thermal andphysical stability of a corresponding uncoated viscoelastic solid. 5.The anti-blocking composition of claim 4, wherein said surfactant ispresent in about 0.5 to about 10.0 weight % based on the totalcomposition.
 6. The anti-blocking composition of claim 4, wherein saidwater-soluble polymeric material is present in about 0.2 to about 5.0weight % based on the total composition.
 7. The anti-blockingcomposition of claim 4, wherein said wetting agent is present in about0.05 to about 0.50 weight % based on the total composition.
 8. Theanti-blocking composition of claim 1, wherein said at least one wax hasa weight average molecular weight of about 1000 to about 15000 Daltons.9. The anti-blocking composition of claim 1, wherein said wax isselected from the group consisting of polyethylene homopolymers,oxidized polyethylene homopolymers, ethylene-vinyl acetate copolymers,ethylene-acrylic acid copolymers, maleic anhydride-grafted polyethylene,maleic anhydride-grafted polypropylene and mixtures thereof.
 10. Amethod of reducing blocking of a viscoelastic solid, comprising thesteps of: a) treating the surface of a viscoelastic solid aftermanufacture with the anti-blocking composition of claim 1; and b)drying; thereby providing a viscoelastic solid coated with saidanti-blocking composition components.
 11. The method of claim 10,wherein said wax is selected from the group consisting of polyethylenehomopolymers, oxidized polyethylene homopolymers, ethylene-vinyl acetatecopolymers, ethylene-acrylic acid copolymers, maleic anhydride-graftedpolyethylene, maleic anhydride-grafted polypropylene and mixturesthereof.
 12. The method of claim 10, wherein said viscoelastic solid isselected from the group consisting of a hot melt adhesive, a hot meltpressure-sensitive adhesive, a hot melt paint and a thermoplasticelastomer.
 13. The method of claim 10, wherein said anti-blockingcomposition is in the form
 14. A coated viscoelastic solid resistant toblocking which is the product of the method of claim 10, wherein thesurface of said viscoelastic solid is coated with an anti-blocking waxor mixture of waxes, and one or more of: a. a surfactant, b. awater-soluble polymeric material, and c. a wetting agent; wherein themolten state of said coated viscoelastic solid retains the thermal andphysical stability of a corresponding uncoated viscoelastic solid. 15.The coated viscoelastic solid of claim 14, wherein the surfactant ispresent in about 0.002 to about 0.25 weight % based on the total weight.16. The coated viscoelastic solid of claim 14, wherein the water-solublepolymeric material is present in about 0.001 to about 0.15 weight %based on the total weight.
 17. The coated viscoelastic solid of claim14, wherein the wetting agent is present in about 0.0002 to about 0.01weight % based on the total weight.